In manufacturing of semiconductor apparatuses, lithography for optically reduction-transferring various patterns formed on a mask onto a wafer is utilized. As extremely high accuracy is required for mask pattern drawing used in the lithography, an electron beam exposure apparatus is used for this purpose. Further, even in a case where a pattern is directly drawn on a wafer without mask, the electron beam exposure apparatus is used.
The electron beam exposure apparatus includes a point beam type apparatus which uses a beam in spot, a variable rectangular beam type apparatus which uses a beam having a variable-size rectangular cross-section, and the like.
These electron beam exposure apparatuses generally have an electron gun unit to generate an electron beam, an electron optical system to guide the electron beam emitted from the electron gun unit onto a sample, a stage system to scan the entire surface of the sample with the electron beam, and an objective polarizer for positioning the electron beam on the surface of the sample with high accuracy.
As electron-beam positioning response is extremely high, generally, the system is constructed with emphasis on measurement of a shift amount of the posture and/or position of the stage to feed back the measured positional shift amount to electron beam positioning by the polarizer to scan the electron beam, rather than on improvement of the mechanical control characteristic of the stage. Further, as the stage is provided in a vacuum chamber and variation of magnetic field which influences the electron beam positioning must be prevented, the conventional stage, simply moved in a plane direction, comprises limited contact-type mechanism elements such as a rolling guide and a ball-screw actuator.
Such contact-type mechanism elements cause a problem of lubrication and a problem of dusting. To solve these problems, Japanese Published Unexamined Patent Application No. Hei 11-194824 discloses a non-contact type 6 freedom stage using an electromagnet actuator and a magnetic shield. According to this system, as a leak magnetic field from the electromagnet is blocked by the magnetic shield, the variation of leak magnetic field is small, and high clean environment can be ensured, and further, a high-accuracy positioning operation even in a vacuum environment can be realized.
However, in the non-contact type 6 freedom stage using electromagnet actuator and magnetic shield, as the structure of the magnetic shield is complicated, the thickness of the magnetic shield portion increases the weight of the stage. For this reason, in the lithography to respond to requirements of higher accuracy and speed, it is difficult to provide a stage to attain high acceleration/deceleration and high-speed positioning.
To realize a future high-speed stage driving (high acceleration/deceleration and high-speed positioning), it is effective to reduce the weight of the stage.
Accordingly, there is an increasing need for a light-weight magnetic shield. Especially, it is desired that the leak magnetic field is reduced by improving drive control of the electromagnet actuator so as to realize the resulting simplification and weight reduction of the magnetic shield.